1. Field of the Invention
The present invention relates to an original feeding apparatus for feeding an original document to an exposure position and ejecting said original after exposure operation.
2. Description of the Prior Art
An automatic original feeding device is often employed in combination with an image forming apparatus such as copier.
Such device is used for example for enabling to copy an original printed on both faces thereof. However such conventional device involves complicated operations for achieving two-side copying with complicated signal transfer between the copier and the device attached thereto, thus inevitably leading to an increase in the number of signal lines, a complicated structure and a deteriorated reliability. Also a change in the specifications of the copier inevitably requires a change in the specifications of the attached device.
On the other hand, a simplified structure, if selected, prohibits the selection of various modes such as two-side copying from a two-sided original and two-side copying from a one-sided original.
Also in a two-side original feeding device, one of stacked plural two-side originals is supplied and stopped in a determined position on an original supporting glass of the copier or the like, and it is guided through a path different from the path of the above-mentioned supply in order to supply said original in inverted position again to the determined position on said original supporting glass, so that the two-side original is subjected to so-called switchback motion, namely a shift from forward motion to backward motion at the switching of the transport paths.
At such switchback operation the original often escapes the supporting rollers or assumes a diagonal position to the transport path, and the apparatus has to be made bulkier if a securer supporting mechanism is employed for avoiding the above-mentioned drawbacks.
Also in case of employing such original circulating device in combination with a two-side copier for making two-sided copies from plural one-side originals, it has been necessary to adopt different operating modes according to whether the number of pages of the originals is even or odd, in order that the pages are orderly arranged. In such device, therefore, it has been customary to once circulate the originals through the device prior to the copying operation in order to count the number of pages and to determined whether it is even or odd. Such method of use, however, not only requires unnecessarily long time for copying but also increases the probability of causing damages in the originals.
Also in case of employing such original circulating device for making plural sets of copies with orderly arranged pages, it has been necessary to circulate the originals plural times. Such operation requires excessively long copying time and tends to generate damages or jammings of the originals.
Besides, the electric power for such device is usually supplied from the copier itself, within the spare capacity of the power supply thereof. However, in recent years, the power supply to the attached device such as the original feeder is being gradually reduced since the above-mentioned spare capacity is being utilized for improving the performance, such as copying speed, of the copier. On the other there exists a contradicting requirement that an increased electric power supply is needed by the attached device in order to achieve highly advanced performance matching that of the copier itself. For this reason the designing of the entire system has become extremely difficult and cannot sometimes be brought to the commercial products.
Also, such device is usually composed of plural original transport means driven by separate power sources, a clock generator functioning in response to one of the transport means, plural original detectors etc. Thus, if the detection for example of the original size is conducted in the course of original transport by counting the clock signals from the clock generator, exact detection cannot be expected by the counting of one specy of clock signals since the amount or speed of movement of the original depends on the speed of each of said plural transport means.